Chain of Custody Violations in Your DWI Case

April 14th, 2021 by Tad Nelson in DWI

In Texas, when physical evidence is collected at the scene of an alleged crime, that evidence must be marked, stored, transported, and collected in a certain way. Law enforcement officers, for instance, must be able to demonstrate that any evidence they collected wasn’t corrupted, mixed-up, or lost and was accounted for during collection, transportation, and storage. This is known as the chain of custody and applies to all evidence, including blood samples taken from those who are suspected of driving while intoxicated (DWI). 

Proving that law enforcement officers didn’t abide by this requirement can be crucial in getting a case dismissed. This is not, however, the only defense at the disposal of those who are facing DWI charges, so if you were arrested for, accused of, or charged with DWI in Texas, it is important to contact an experienced Houston DWI lawyer who can walk you through your options. 

Chain of Custody Requirements

Law enforcement officers are always required to comply with chain of custody requirements when gathering evidence for a criminal case. These same rules apply to DWI cases, where prosecutors will need to provide:

  • Chain of custody documentation;
  • A video recording of the blood sample collection;
  • Data printouts from the laboratory test;
  • Records indicating compliance with standard hospital procedures; and
  • Records related to the calibration of testing equipment. 

Poor documentation of the blood draw, or the transportation of a sample to the lab, could significantly weaken a prosecutor’s case, as could a lack of documentation showing that a sample was properly handled and managed while it was in police custody. Ultimately, for a prosecution to be successful, the state will need to prove who had possession of the sample from the time of its collection to the introduction of trial proceedings. Any break in this chain could be evidence of a serious error. 

Proving the Origin of the Test Sample

Chain of custody rules also apply to blood tests used in the prosecution of DWI cases, where blood samples must be carefully taken, labeled, stored, and transported without contamination. For instance, when filing these kinds of charges in court, prosecutors must be able to prove that the blood tested (to determine a driver’s BAC level at the time of arrest) is the same as the blood that was drawn from the driver in a DWI case. When proving this, the state cannot merely rely on medical records to prove that a test result belonged to a defendant, but must also be able to show the chain of custody of the sample. 

Call Today for Legal Representation

A skilled defense attorney can challenge a prosecutor’s claims regarding the chain of custody of a blood sample and could even get that evidence excluded. If you or a loved one are facing DWI charges and believe that the evidence wasn’t properly collected, transported, stored, or tested, please call 281-280-0100 to speak with one of the experienced Houston DWI lawyers at The Law Offices of Tad Nelson & Associates about pursuing this defense.

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